Behavior of Earthquake-Resistant Rectangular Walls with Mechanically Spliced Grade 100 Steel Bars

Three large-scale reinforced concrete (RC) rectangular slender structural walls were subjected to cyclic displacement demands to establish whether, and under what conditions, mechanical splices can be used with Grade 100 (690) bars where yielding is expected. These tests were conducted because ACI 318-19 prohibits both lap splices and mechanical splices for high-strength longitudinal reinforcement (Grade 80 [550] and higher) in special structural walls where yielding is expected. Three mechanical splices were used that differed in connection type (one type per wall) and overall splice length. All longitudinal bars were mechanically spliced starting 2 in. (50 mm) from the wall base. Mechanical splices satisfying the specified minimum tensile strength criterion of ACI 318-19 Type 2 mechanical splices resulted in better wall behavior than reported for lap splices, but satisfying Type 2 requirements alone did not prevent bar fractures at the mechanical splice. Thus, Type 2 mechanical splice requirements are not recommended as the sole qualification criteria where yielding is expected. Test results also showed that mechanical splices with a strength not less than the actual bar tensile strength, such that bars systematically fail in direct tension tests away from the splice and therefore develop their actual uniform elongation, perform well and are recommended for use where yielding is expected in special structural walls.